I was somewhat cynical earlier but I think I should thank you for posting this. I'm not sure that it will affect our behaviour very much, but it's always better to be aware of the facts & thus able to make an informed decision rather than sleep-walking.

Building regs in the UK stipulate for new builds that if you live in a Radon affected area you are obliged to install a Radon barrier and a passive sump if you have a solid slab bearing on the ground or a barrier and air bricks every 2m around the perimeter of a suspended floor. In older buildings you are not obliged to take any action at all. A perfect barrier works perfectly however it's not uncommon for the barrier to be compromised during the build process with holes being cut for services and general abrasion by builders boots etc so that is why a sump is also specified for stabbed properties as a backup for failed barriers. When the build is complete a Radon test can be commissioned and if the radon levels are still high then the passive sump can be converted into an active sump by the addition of a fan which can enable dramatic reductions. Building regs are very important but if there is insufficient diligence during the build process then failure results. Unfortunately many new builds fail their first test whether they have suspended or solid floors.It's costs about £50 to have a Radon test and if you live in a Radon affected area it is recommended you do so by every national health agency and the WHO. I think it's a relatively small cost and it enables the house holder to make an informed decision about their position and whether they wish to do anything about it.I would add that in the UK the HSE stipulates that all workplaces in Radon affected areas must carry out testing and reduce levels to below 400bq.V

Venatore has told me a load of really interesting stuff about radon, and how it can enter your house through fissures in a ground slab, and how it can be easily counteracted

I'd just like to point out that (afaik national Italian) buiding regs insist on a ventilated cavity between a habitable 'ground floor' and the real ground. So, while if you have an 'unrestored' and unventilated cantina, (with a fissured floor in contact with 'radon prone' ground), there is a remote possibility that radon gas could enter your first floor living spaces.

Or, if you are using ground floor spaces as habitation, without having complied with the requirement for sub-floor ventilation, then clearly radon gas could become a relevant consideration in those ground floor rooms.

In new build in Italy (I think also in the UK) the norm is for a 'suspended' ground floor, which isolates the habitable ground floor from the underlying geology. BUT, as always, builders want to keep it cheap, and if I was worried about radon gas infiltration I wouldn't be very sanguine about the 'granchio' solution so frequently (and entirely legally) adopted in Italy.

But, overall, I do favour the 'not worry about it' position taken by many posters. You are either going to get hit by a terrorist (like a 1 i n a million chance) or you get slowly poisoned by radon gas. Or you don't.